When a customer who subscribes for call-waiting (hereinafter sometimes referred to as conventional call-waiting or CW) service is engaged in a telephone conversation with a second party and a third party calls that customer, the customer receives a special call-waiting signal while the third party receives audible ringing. If the call-waiting customer desires to receive the call from the third party, a switchhook flash will hold the second party while the subscriber's connection is switched to the third party. If the call-waiting signal is ignored, a second call-waiting signal is given after a few seconds.
Heretofore, call-waiting service has been illustrated in connection with both electromechanical and stored program controlled switching systems. Early versions of call-waiting service, such as that shown in Zarouni U.S. Pat. No. 3,133,995 required that auxiliary line terminals be provided for each line subscribing for call-waiting service. Later versions, such as those shown in Pommerening, et al. U.S. Pat. No. 3,963,874, George et al. U.S. Pat. No. 3,997,731, and R. V. Beth U.S. Pat. No. 3,584,156 either eliminated the need for a preassigned additional network line appearance or extended the call-waiting concept to program controlled switches in which certain custom calling features could be implemented by making changes in memory assignment.
As a further refinement of call-waiting service, Sheinbein U.S. Pat. No. 4,277,649 taught that, if the calling line's identity were forwarded to the switching office containing the called customer's service feature memory, that memory could be interrogated prior to completing the call to ascertain the call disposition based on the information that had been priorly inserted into the service feature memory by the called customer.
A variety of such control prior to the establishment of any telephone connection has enabled a customer subscribing for call-waiting service to cancel the call-waiting feature until later re-activated by the customer. This type of service has been known as "cancel call-waiting" or CCW service.
While each of the foregoing architectures implements a useful version of call-waiting service, telephone users continue to express some degree of dissatisfaction with the inflexible way in which call-waiting service operates.
When a call-waiting subscriber decides to ignore the call-waiting signal because the customer does not want to interrupt the conversation, not only must that customer experience the annoyance of the second or "reminder" call-waiting signal, but when that tone is subsequently ignored, the third party continues to receive audible ringing. Since the receipt of audible ringing is generally understood to be inconsistent with the called line being busy, the third party may be misled into believing that the called line is unattended. For this reason, the call-waiting customer who does not want to interrupt the existing connection may, nevertheless, want to indicate to the third party either that the line is truly busy or that the present conversation will be terminated in a short time. While pre-recorded announcements or rerouting have heretofore been available to treat third party calls prior to the establishment of the calling connection, the call-waiting subscriber has not heretofore been able selectively to direct the type of treatment to by given to the third party call during the continuance of his original conversation.